package classExample;
import java.util.Scanner;

public class AreaOfCircle {
    public static void main(String[] args)
    {
        double radius,area;
        Scanner in = new Scanner(System.in);
        radius = in.nextDouble();
        area = Math.PI*radius*radius;
        System.out.println("圆的面积为: "+area);
    }
}
